Various apparatus have heretofore been proposed for correcting deviation or zigzag travel of running sheets. For example, an apparatus is known which comprises a hollow cylindrical member rotatably supported on a shaft, a plurality of guide bars mounted on the cylindrical member as arranged radially therearound and slidable each in its axial direction, and an annular guide plate composed of two rings for supporting one end of each guide bar by a bracket and a roller. Zigzag travel of a running sheet can be corrected by the axial sliding movement of the guide bars effected by inclination of the guide plate and revolution of the guide bars around the shaft. An outer peripheral portion of the guide plate is pivotably supported by a support member, while another outer peripheral portion of the guide plate diametrically opposed to the portion is connected to an operating device comprising a cylinder. The guide plate can be inclined about the point where it is pivotably supported, by the advance or retraction of the operating device.
However, the apparatus, in which the support point for the inclination of the guide plate is specified, has the following limitations in correcting zigzag travel of the running sheet.
This type of correcting apparatus generally has responsiveness to immediately correct the position of the running sheet upon deviation of the sheet and also a tendency to act in a sustained fashion, i.e. to gradually correct the position of the sheet in a definite direction. When the support point for the guide plate is remote from the apparatus, the apparatus has high responsiveness, whereas if it is close to the apparatus, the apparatus acts in the sustained fashion.
Nevertheless, when the guide plate has a definite support point for inclination, it is impossible to adjust the responsiveness and the sustained action, with the result that difficulty is encountered in correcting zigzag travel of the running sheet accurately. Further if the support point is set at a remote position for higher responsiveness, there arises the problem that the apparatus becomes bulky and requires a larger space for installation.